U.S. patent application number 11/643294 was filed with the patent office on 2008-06-26 for polysiloxane modified titanium dioxide.
Invention is credited to Christopher J. Drury, Robert J. Kostelnik, Charles A. Wheddon.
Application Number | 20080152914 11/643294 |
Document ID | / |
Family ID | 39543278 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080152914 |
Kind Code |
A1 |
Kostelnik; Robert J. ; et
al. |
June 26, 2008 |
Polysiloxane modified titanium dioxide
Abstract
A particle of titanium dioxide treated with a polysiloxane is
disclosed. One or more silicon atoms of the polysiloxane are
substituted with an alkylene group that is terminated with a silyl
group containing three substituents selected from the group
consisting of hydroxy, halo, alkoxy, acetoxy, and mixtures thereof.
These treated particles are blended with organic polymers.
Inventors: |
Kostelnik; Robert J.;
(Ellicott City, MD) ; Drury; Christopher J.;
(Ulceby, GB) ; Wheddon; Charles A.; (Tetney,
GB) |
Correspondence
Address: |
KING & SPALDING
1185 AVENUE OF THE AMERICAS
NEW YORK
NY
10036-4003
US
|
Family ID: |
39543278 |
Appl. No.: |
11/643294 |
Filed: |
December 21, 2006 |
Current U.S.
Class: |
428/407 ;
106/445; 428/402; 524/413 |
Current CPC
Class: |
C08K 9/06 20130101; Y10T
428/2982 20150115; C01G 23/047 20130101; C09C 1/3684 20130101; Y10T
428/2998 20150115; Y10T 428/2993 20150115; C01P 2004/62 20130101;
C09C 1/3653 20130101; C09C 1/3692 20130101 |
Class at
Publication: |
428/407 ;
106/445; 428/402; 524/413 |
International
Class: |
B32B 5/16 20060101
B32B005/16; C08K 3/10 20060101 C08K003/10 |
Claims
1. A particle comprising titanium dioxide treated with a
polysiloxane wherein one or more silicon atoms of the polysiloxane
are substituted with an alkylene group that is terminated with a
silyl group containing three substituents selected from the group
consisting of hydroxy, halo, alkoxy, acetoxy, and mixtures
thereof.
2. The particle of claim 1 wherein the polysiloxane has the general
formula: ##STR00006## wherein each of R.sub.1 and R.sub.2 is
independently selected from the group consisting of C.sub.1 to
C.sub.14 hydrocarbyl; each R.sub.3 is selected from the group
consisting of hydroxy, halo, alkoxy, and acetoxy; R.sub.4 is
selected from the group consisting of C.sub.1 to C.sub.22
hydrocarbyl; x is an integer from 1 to 22; m is an integer from 0
to 500; and n is an integer from 1 to 500.
3. The particle of claim 2 wherein R.sub.3 is alkoxy.
4. The particle of claim 2 wherein R.sub.3 is hydroxy.
5. The particle of claim 2 wherein R.sub.4 is C.sub.6 to C.sub.10
hydrocarbyl.
6. The particle of claim 2 wherein the sum of m+n is greater than
12.
7. The particle of claim 2 wherein m is greater than n.
8. The particle of claim 1 wherein the weight ratio of polysiloxane
to titanium dioxide is from 0.0001:1 to 0.5:1.
9. The particle of claim 1 wherein the weight ratio of polysiloxane
to titanium dioxide is from 0.001:1 to 0.02:1.
10. The particle of claim 1 having a mean particle diameter of from
0.2 to 0.35 microns.
11. The particle of claim 1 having a mean particle diameter of less
than 0.2 microns.
12. The particle of claim 1 wherein the titanium dioxide is treated
with at least one coating material prior or subsequent to treatment
with the polysiloxane.
13. The particle of claim 12 wherein the coating material is
selected from the group consisting of aluminum oxide, silicon
dioxide, zirconium oxide, inorganic phosphates, acid-soluble
titanium dioxide, alkanolamines, and polyalcohols.
14. A process to prepare the particle of claim 1 wherein the
polysiloxane is added to the titanium dioxide in a mixing
device.
15. The process of claim 14 wherein the polysiloxane is added as an
aqueous emulsion.
16. A composition comprising the particle of claim 1 and an organic
polymer.
17. The composition of claim 16 wherein the organic polymer is
selected from the group consisting of polyethylenes,
polypropylenes, polystyrenes, polycarbonates, polyvinylchlorides,
and copolymers of ethylene and C.sub.4-12 .alpha.-olefins.
18. The composition of claim 17 wherein the organic polymer is
polyethylene.
19. The composition of claim 16 further comprising zinc sulfide,
barium sulfate, calcium carbonate, and combinations thereof.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a particle obtained by treating
titanium dioxide with a polysiloxane. Blends of these particles
with organic polymers are disclosed.
BACKGROUND OF THE INVENTION
[0002] Titanium dioxide has found widespread use. Typically it is
used in another matrix to impart certain properties. For example,
it is widely used as a white pigment for paints and polymers. Other
applications use small particle titanium dioxide which has
different optical properties. For these and other applications, it
is critical to have good dispersion of the titanium dioxide.
Dispersing agents are often added to the titanium dioxide.
Selection of the dispersing agent is often a compromise between
effectiveness, cost, compatibility with other additives in the
matrix, and performance properties in the matrix. For this reason,
much work has been done to improve the dispersion of titanium
dioxide in various matrices.
[0003] A variety of treatments has been studied. U.S. Pat. No.
6,646,037 treats the titanium dioxide with alkyl sulfonic acid
salts and U.S. Pat. No. 6,765,041 discloses treatment with alkyl
phosphate esters. Organosilicon compounds have been used. For
instance, U.S. Pat. No. 4,061,503 discloses the treatment of
particulate titanium dioxide with a polyether-substituted silicon
compound for improving the dispersibility of titanium dioxide in
pigmented and/or filled paints and plastics, and reinforced plastic
composite compositions.
[0004] U.S. Pat. No. 4,810,305 discloses an organopolysiloxane with
improved dispersibility. The polysiloxane is a hydrosiloxane such
as polymethylhydrosiloxane. U.S. Pat. Nos. 5,607,994, 5,631,310,
5,889,090, and 5,959,004 disclose the use of a mixture of a
hydrolyzable silane such as butyltrimethoxysilane and a
polysiloxane such as polydimethylsiloxane. U.S. Pat. No. 5,932,757
describes a mixture of oligomers of alkylalkoxysilanes.
[0005] U.S. Pat. No. 6,620,234 discloses mixing a reactive
chlorosilane such as hexyl trichlorosilane with titanium dioxide in
an aqueous media to form coated titanium dioxide. The byproduct
hydrochloric acid is neutralized and removed as a salt.
[0006] While there have been much research regarding the coating of
titanium dioxide with silanes and siloxanes, further improvements
are needed. To date, treatment techniques are often a compromise
between processability and final properties. Many
silicon-containing compounds are not sufficiently reactive with
titanium dioxide to provide effective coatings. Other
silicon-containing compounds are either volatile or produce
volatile side products. In an effort to improve reactivity,
functional groups such as alkoxy groups have been used, but the
alcohol generated as a byproduct can cause environmental issues
during pigment production. Use of halosilanes in aqueous media can
solve this problem, but it is a more complicated process and adds
to the cost. Despite the significant research done in this area,
there is a need for further improvements.
SUMMARY OF THE INVENTION
[0007] The invention is a particle and blends of these particles
with organic polymers. The particle is obtained by treating
titanium dioxide with a polysiloxane. One or more silicon atoms of
the polysiloxane are substituted with an alkylene group that is
terminated with a silyl group containing three substituents
selected from the group consisting of hydroxy, halo, alkoxy,
acetoxy, and mixtures thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0008] The invention is a particle and blends of these particles
with organic polymers. The particle is obtained by treating
titanium dioxide with a polysiloxane. Any form of titanium dioxide
is suitable for the particle of the invention. Preferably, the
titanium dioxide is in the rutile or anatase form. The titanium
dioxide can be prepared by any known process, such as the sulfate
process or the chloride process.
[0009] The titanium dioxide useful in the invention has a typical
particle size in the range of 0.001 to 20 .mu.m. For use in typical
pigmentary applications, the titanium dioxide preferably has a
particle size in the range of from 0.1 to 0.5 .mu.m, more
preferably from 0.2 to 0.35 .mu.m. For use in photocatalytic
applications, the titanium dioxide preferably has a particle size
in the range of from 0.001 to 0.1 .mu.m.
[0010] The titanium dioxide may be untreated titanium dioxide
obtained directly from a production process such as the chloride or
sulfate processes. Alternatively, the titanium dioxide may be
treated with at least one coating material prior or subsequent to
treatment with the polysiloxane of the present invention. Suitable
coating materials include inorganic oxides, such as aluminum oxide,
silicon dioxide, zirconium oxide, inorganic phosphates,
acid-soluble titanium dioxide, and the like. Suitable organic
coating materials include polyalcohols such as trimethylolpropane
and alkanolamines, such as triethanolamine. Preferably, the
titanium dioxide is coated with alumina. The amount of alumina is
preferably 0.01-0.8% by weight in terms of Al.sub.2O.sub.3 relative
to TiO.sub.2. Processes to deposit metal oxides onto a titanium
dioxide are well known to those skilled in the art. Preferably, the
metal oxides are added by wet treatment or by gas-phase deposition.
Suitable wet treatment techniques are taught in U.S. Pat. Nos.
3,767,455, 4,052,223, and 6,695,906, the teachings of which are
incorporated herein by reference. Suitable gas-phase deposition
techniques are taught in U.S. Pat. Nos. 5,562,764 and 6,852,306,
the teachings of which are incorporated herein by reference.
[0011] The titanium dioxide is treated with a polysiloxane. One or
more silicon atoms of the polysiloxane are substituted with an
alkylene group that is terminated with a silyl group containing
three substituents selected from the group consisting of hydroxy,
halo, alkoxy, acetoxy, and mixtures thereof.
[0012] Preferably, the polysiloxane has the general formula:
##STR00001##
[0013] wherein each of R.sub.1 and R.sub.2 is independently
selected from the group consisting of C.sub.1 to C.sub.14
hydrocarbyl; each R.sub.3 is selected from the group consisting of
hydroxy, halo, alkoxy, and acetoxy; R.sub.4 is selected from the
group consisting of C.sub.1 to C.sub.22 hydrocarbyl; x is an
integer from 1 to 22; m is an integer from 0 to 500; and n is an
integer from 1 to 500. Preferably, R.sub.3 is selected from the
group consisting of hydroxy and alkoxy. Preferably, R.sub.4 is
C.sub.6 to C.sub.10 hydrocarbyl. Preferably, R.sub.1 is methyl.
Preferably, the sum of m+n is greater than 12, more preferably,
greater than 20. Preferably, m is greater than n and more
preferably greater than 3n.
[0014] The polysiloxane can be made by any method. One convenient
method is to combine the cyclic precursors in an acid or base
catalyzed reaction. For example:
##STR00002##
[0015] The cyclic monomer containing the silane can be prepared by
any method. One convenient method is from a hydrosiloxane and a
silane as shown below:
##STR00003##
[0016] This method is described in U.S. Pat. No. 6,660,822, which
is incorporated herein by reference.
[0017] Titanium dioxide is treated with the polysiloxane. The
polysiloxane may be added neat, as a solution, or as an emulsion.
Preferably, the polysiloxane is added neat or as an aqueous
emulsion. The methods for adding the polysiloxane may be similar to
methods for adding other surface treatments that are flexibly and
easily incorporated into titanium dioxide production processes.
Thus, there are many places during production of titanium dioxide
in which the polysiloxane may be added and the points of additions
described herein are not meant to be exhaustive. The optimal point
during which to add the polysiloxane will in part depend on the
process in which it is to be incorporated.
[0018] In the simplest of methods, the polysiloxane may be added by
spraying or pouring into a system in which the titanium dioxide is
already present. To maximize the uniformity of the distribution of
the polysiloxane, preferably, a mixing device is used to mix or to
stir the polysiloxane and the titanium dioxide. Devices such as a
V-shell blender equipped with an intensifier bar for application of
a liquid to a powder or other suitable mixing devices now known or
that come to be known to those skilled in the art may be used.
[0019] One preferred mixing device is a micronizer. The
polysiloxane may be metered into a micronizer or jet pulverizer
along with the titanium dioxide powder to be ground. Air or steam
micronization techniques may be used at temperatures from room
temperature up to 250.degree. C. or higher.
[0020] In a conventional production process, the polysiloxane may,
by way of further example, be added to the spray drier feed or
repulped filter cake, to a high intensity milling device or to a
micronizer feed prior to or concurrent with micronization. In other
titanium dioxide processes, it may be desirable to add the
polysiloxane to a fluidized, washed filter cake with agitation in
order to assure uniform mixing of the polysiloxane among the
titanium dioxide particles. Further, in some embodiments, it is
desirable to add the polysiloxane after any filtration and washing
stages, but prior to any drying stage.
[0021] If the polysiloxane is added to a dry titanium dioxide such
as a spray drier product or micronizer feed, particular care should
be taken to ensure uniform mixing of the polysiloxane with the
titanium dioxide powder. This may, for example, be accomplished by
using a V-shell blender equipped with an intensifier bar or by
using other suitable mixing devices. After the polysiloxane has
been combined with the titanium dioxide, the treated titanium
dioxide may be fluid energy milled using steam or air to produce a
treated, finished titanium dioxide.
[0022] Preferably, the weight ratio of polysiloxane to titanium
dioxide is from 0.0001:1 to 0.5:1 and more preferably from 0.001:1
to 0.02:1.
[0023] For use in pigmentary applications, preferably the particle
of titanium dioxide treated with the polysiloxane has a mean
particle diameter of from 0.2 to 0.35 microns. For certain other
applications, preferably the particle has a mean particle diameter
of less than 0.2 microns.
[0024] The particle of titanium dioxide treated with the
polysiloxane can be blended with an organic polymer. Preferably,
the treated titanium dioxide is dry blended with the organic
polymer and then mixed in the melt. This can be done, for example,
by using a Banbury mixer or a twin screw extruder. The amount of
treated titanium dioxide used will vary dependent upon the final
application. One convenient technique is to first prepare a
concentrate of the treated titanium dioxide with the organic
polymer and then mix the concentrate with more organic polymer to
achieve the desired weight ratio.
[0025] Any organic polymer may be used. Preferably, the organic
polymer is selected from the group consisting of polyethylenes,
polypropylenes, polystyrenes, polycarbonates, polyvinylchlorides,
and copolymers of ethylene and C.sub.4-12 .alpha.-olefins. More
preferably, the organic polymer is polyethylene. Dependent upon the
application, the composition of treated titanium dioxide and
organic polymer can contain other additives, fillers, and pigments.
Zinc sulfide, barium sulfate, calcium carbonate, and combinations
thereof are preferred pigments for use in the composition.
[0026] The following examples merely illustrate the invention.
Those skilled in the art will recognize many variations that are
within the spirit of the invention and scope of the claims.
EXAMPLE 1
Titanium Dioxide Modified with Siloxane 1
##STR00004##
[0028] Sodium aluminate (30.8 mL of a 343 g Al.sub.2O.sub.3/L
aqueous solution) is added to an aqueous slurry of 5,000 grams of
fine particle chloride process rutile titanium dioxide (350 g
TiO.sub.2/L) with mixing at 70.degree. C. The slurry pH is adjusted
to 7.0 using a concentrated hydrochloric acid (aqueous) solution,
and the slurry is allowed to age for 30 minutes with stirring. The
aged slurry is filtered and washed twice with 5000 mL aliquots of
80.degree. C. deionized water, and then dried overnight at
110.degree. C. in an oven. The dried filter cake (0.2%
Al.sub.2O.sub.3 on TiO.sub.2) is forced through an 8-mesh screen in
preparation for treatment with organics.
[0029] A portion of the dry, 8 mesh, alumina-coated TiO.sub.2 (1000
g) is spread to a 1 cm thickness on polyethylene film and Siloxane
1 (12.2 g; molecular weight=5,400 g/mol; molar ratio of m/n=19:1)
is added dropwise in a circular motion to give a 1.2% loading
level. The pigment is mixed with a large spatula and transferred to
a one gallon wide-mouth Nalgene bottle. The bottle containing
pigment is rolled for 10 minutes on a roller mill. The rolled
pigment is steam micronized to produce the finished pigment.
[0030] The finished pigment (125 g) is dry blended with low density
polyethylene (125 g of LDPE 722 available from Dow Chemical
Company) and added to a 75.degree. C. preheated chamber of a Haake
3000 Rheomix mixer with rotors running at 50 rpm. One minute after
addition of the blend, the chamber temperature is raised to
105.degree. C. Frictional heat generated by the mixing process is
allowed to drive the rate of incorporation of the TiO.sub.2 into
the LDPE until a steady state mixture is achieved. The concentrate
is removed from the mixing chamber and placed into a Cumberland
Crusher to obtain finely granulated 50% concentrate samples. The
granulated concentrates are conditioned for 48 hours at 23.degree.
C. and 50% relative humidity. The concentrate is then let down into
LDPE to achieve a 20% loading of TiO.sub.2 in the final film.
[0031] Lacing evaluations are run on a 25 mm extruder equipped with
a cast film slot die. A temperature profile of 330.degree. C. die,
270.degree. C. clamp ring, 215.degree. C. zone 3, 175.degree. C.
zone 2, and 150.degree. C. zone 1 is used. The screw speed is set
at about 90 rpm. A 25.4 cm polished chrome chill roll, set in
conjunction with the extruder is used to maintain a 75 micron film
thickness, and to cool and transport the films. The chill roll
distance from the die lips is about 22 mm and the temperature is
about 27.degree. C.
[0032] After the TiO.sub.2/LDPE mix is placed in the hopper, the
material is allowed to purge until the appearance of a white tint
in the film is first noted. To ensure the concentration of
TiO.sub.2 in the film has stabilized, a time interval of two
minutes is allowed before lacing observations are recorded and a
film sample obtained. Lacing performance is determined by counting
the relative size and number of holes generated in a film sample
laid out on a dark surface. A 1.0-3.0 rating system is used. A
rating of 1 is given to films with no lacing, 2 is given to films
showing the onset of lacing and 3 is given to films with extreme
lacing. Increments of 0.1 are used to give an indication of the
relative performance between the samples. The film had a rating of
1.0 indicating low volatility and excellent temperature
stability.
[0033] Using a small-scale laboratory extrusion apparatus, a
measure of particulate inorganic solid dispersion into organic
polymers is obtained by measuring the relative amount of
particulate inorganic solid trapped onto screens of extruder screen
packs. Tests are made using 75% TiO.sub.2 concentrates in low
density polyethylene prepared using a Haake 3000 Rheomix mixer. The
mixer is controlled and monitored with a Haake 9000 Rheocord Torque
Rheometer.
[0034] A 75% concentrate is made by dry blending the finished
pigment (337.7 g) and LDPE (112.6 grams NA209 available from
Equistar Chemicals) and adding the blend to a 75.degree. C. mixing
chamber with rotors operating at 50 rpm. The mixer temperature is
programmed to increase to 120.degree. C. one minute after the dry
blend is introduced to the mixing chamber. After a steady state
mixture is achieved, the compound is mixed for an additional 3
minutes. The compound is removed from the chamber and granulated
using a Cumberland crusher.
[0035] Dispersion tests are conducted using a Killion single screw
extruder, model KL-100 equipped with a 20:1 length to diameter
screw. The extruder is preheated at 165, 175, 200, 195.degree. C.
from zone 1 to the die, respectively, and operated at 70 rpm. A
purge of 1000 g of LDPE is run through the system, and a new screen
pack is installed. The screen pack consisted of 40/500/200/100 mesh
screens from the die towards the extruder throat. After temperature
stabilization, the granulated 75% concentrate (133.3 g) is fed into
the extruder. This is followed with 1500 g of LDPE purge as the
feed hopper empties. After the LDPE purge is extruded, the screens
are removed, separated and tested using a relative count technique
from the measurements from an X-ray fluorescence spectrometer. The
number of TiO.sub.2 counts per second is obtained for the 100, 200
and 500 mesh screens in the pack and totaled to obtain the
dispersion result. Lower TiO.sub.2 counts per second are desired. A
count result of less than 5000 is considered to represent excellent
dispersion. The concentrate had 670 counts per second indicating
excellent dispersion.
EXAMPLES 2-4
Titanium Dioxide Modified with Siloxane 1
[0036] In similar fashion as in Example 1, blends are prepared and
evaluated from titanium dioxide modified with siloxane 1 with
different ratios of m and n, with different molecular weights of
the siloxane, and with different loading levels of siloxane. The
conditions and results are shown in Table 1. All show excellent
dispersion, low volatility, and excellent temperature
stability.
EXAMPLES 5-7
Titanium Dioxide Modified with Siloxane 2
##STR00005##
[0038] In similar fashion as in Example 1, blends are prepared and
evaluated from titanium dioxide modified with siloxane 2, which is
added to the titanium dioxide as an aqueous emulsion (50% solids).
The conditions and results are shown in Table 1. All display
excellent dispersion, low volatility, and excellent temperature
stability.
EXAMPLES 8-13
Sulfate Process Titanium Dioxide Modified with Siloxane
[0039] In similar fashion as in Example 1, blends are prepared and
evaluated from titanium dioxide modified with siloxane. Blends are
prepared using sulfate process rutile titanium dioxide with 0.4%
Al.sub.2O.sub.3 on TiO.sub.2. The conditions and results are shown
in Table 1. All show excellent dispersion, low volatility and
excellent temperature stability demonstrating that the benefit of
the siloxanes is general and useful for the modification of
titanium dioxide prepared by the sulfate process.
COMPARATIVE EXAMPLE 14
Titanium Dioxide Modified with Triethanolamine
[0040] In similar fashion as in Example 1, a blend is prepared and
evaluated from chloride process rutile titanium dioxide modified
with triethanolamine, a known modifier, rather than siloxane. The
conditions and results are shown in Table 1. The dispersion is much
worse than found with the siloxane modifiers.
TABLE-US-00001 TABLE 1 Reaction Zone A Conditions Exam- Mol.
Disper- ple Modifier Loading Wt. m/n sion Lacing 1 Siloxane 1 1.2
5,400 19 670 1.0 2 Siloxane 1 0.9 5,600 9 490 1.0 3 Siloxane 1 0.9
5,800 4 430 1.0 4 Siloxane 1 0.9 26,000 19 2,660 -- 5 Siloxane 2
0.75 -- 30 650 1.3 6 Siloxane 2 0.9 -- 30 460 1.3 7 Siloxane 2 0.9
-- 9 480 1.4 8 Siloxane 1 0.9 5,400 19 690 1.1 9 Siloxane 1 1.2
5,600 9 1,360 1.1 10 Siloxane 1 0.9 5,800 4 1,230 -- 11 Siloxane 2
1.1 -- 30 900 1.2 12 Siloxane 2 1.5 -- 30 420 1.4 13 Siloxane 2 1.1
-- 9 490 1.2 C14 Triethanolamine 0.6 -- -- 13,700 1.4
[0041] The preceding examples are meant only as illustrations. The
following claims define the invention.
* * * * *